Browsing by Author "Madina, V."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Compatibility of materials with hydrogen. Particular case: Hydrogen embrittlement of titanium alloys(2009-07) Madina, V.; Azkarate, I.; MATERIALES PARA CONDICIONES EXTREMAS; Tecnalia Research & InnovationA review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials, hydrogen embrittlement, low temperature effects, material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials, the hydride formation of titanium alloys is considered. Hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media have been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials, particularly the β-phase content, plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.Item Materials and hydrogen. Hydrogen assisted stress cracking of titanium alloys(2008-05) Azkarate, I.; Ezponda, E.; Madina, V.; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMASA review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials, hydrogen embrittlement, low temperature effects, material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials, the hydride formation of titanium alloys is considered. Alpha titanium alloys are considered corrosion resistant materials in a wide range of environments. However, hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys, Ti Gr-2, Ti Gr-5 and Ti Gr-12, to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media has been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials, particularly the β phase content, plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.Item Techniques for assessing the protective properties of chromated conversion coatings - Part I: Aluminum(1996) Gilroy, D.; Eddowes, P. J.; Dalrymple, I. M.; Azkarate, I.; Madina, V.; Seco, F.; Del Barrio, A.; Parkes, J.; Byrne, M.; Byrne, R.; Almeida, E. M.; Maia, A.; Pereira, D.; Bentes, F. L.; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMASItem Techniques for assessing the protective properties of chromated conversion coatings - Part II: Galvanized steel(1996) Gilroy, D.; Eddowes, P. J.; Dalrymple, I. M.; Madina, V.; Seco, F.; Del Barrio, A.; Parkes, J.; Byrne, M.; Byrne, R.; Almeida, E. M.; Maia, A.; Pereira, D.; Bentes, F. L.; MATERIALES PARA CONDICIONES EXTREMAS; Tecnalia Research & InnovationItem Zn-Cr alloy coatings produced by ion beam assisted deposition(1998-05) Alonso, F.; Madina, V.; Viviente, J. L.; Mursell, T.; Oñate, J. I.; Centros PRE-FUSION TECNALIA - (FORMER); MATERIALES PARA CONDICIONES EXTREMAS; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Tecnalia Research & InnovationIn the present work, Zn-Cr alloy coating have been deposited on a Ti + Nb interstitial free steel by an IBAD process. Zn was deposited by a resistance-heated evaporation source, while Cr was simultaneously evaporated with an electron beam gun. Low-energy Ar ion beam bombardment was used during the process to sputter-clean the surface prior to deposition and during deposition to obtain a dense coating. Different Zn:Cr evaporation ratios ranging from 30:30 were applied to produce several Zn-Cr alloy coatings until a final coating thickness of about 7 μm was obtained. The process was carried out at room temperature and XRD, which showed a change from the hexagonal Zn structure to a b.c.c. structure as the amount of Cr in the coating increased. Salt spray corrosion tests revealed that increasing the Cr content in the coatings improved significantly the corrosion resistance up to a maximum limit of about 20% wt., beyond which no substantial benefit could be observed. Mandrel bend tests showed a good adhesion of the coating to the substrate, and no delamination or cracks were observed. A dynamic microindentation test also showed the presence of chromium significantly improved the hardness of the Zn coating up to a factor of 5, with a similar effect on the elastic recovery of the indentation.